Vibration and noise control in liquid springs



May 11, 1965 w. T. PRICE ETAL VIBRATION AND NOISE CONTROL IN LIQUID SPRINGS 2 Sheets-Sheet 1 Filed Sept. 13, 1961 INYENTORS Wilson 7. Pr/ce Chang/P. Brown OVCC) BY ATTORNEYS Assn/r y 1955 WI. PRICE ETAL 3,182,987

VIBRATION AND NOISE CONTROL IN LIQUID SPRINGS Filed Sept. 13, 1961 2 Sheets-Sheet 2 IN VFNTORS Wilson 7. PIICQ Charles R. Brown m Jam r:

United States Patent 3,182,987 VHBRATION AND NOISE CONTROL IN LIQUID SPRINGS Wilson T. Price, Santa Clara, and Charles R. Brown,

Sunnyvale, Calif., assignors, by mesne assignments, to

the United States of America as represented by the Secretary of the Navy Filed Sept. 13, 1961, Ser. No. 138,534 3 Claims. (Cl. 267-64) The present invention relates generally to missile launchers and more particularly to means for isolating a missile from vibration.

With the advent of ballistic missiles, the need arose, for a method of making the missile launching complex invulnerable to surprise attack by enemy missiles and aircraft. Without such invulnerability it would be possible for a ballistic missiles capability to be completely destroyed before it could be launched in a retaliatory action. Further, without means to protect these launching complexes from destruction by enemy attack, they would be unable to fulfill their primary role of a deterrent to a possible enemy surprise attack.

Accordingly, several expedients have been the subject of extensive research and development. The three most prominent methods are firstly, the hardening of launching sites, for example, building concrete silos below ground level; secondly, by launching the missile from an airborne aircraft; and thirdly, by launching the missile from a moving ship or land vehicle. This invention finds use primarily in missile launchers of the third category. However, it cannot be said that the invention is inapplicable to the other two categories as it is possible that such a device could be utilized in conjunction with the launching of any ballistic or guided missile.

The missile launching systems which are mounted on vehicles usually are provided with a supply of missiles stored in a position which permits rapid firing. Such vehicles may have a tube-type launching system which includes one or more missile launching tubes, each having a missile positioned therein. The tube acts as a storing and conveying means as well as a launcher. These vehicles from time to time are subjected to substantial structural stressing and consequent structural flexing, and therefore the tube systems may comprise an outer tube which resiliently supports an inner tube in which the missile is positioned. The primary function of this dual tube system is to protect the missile from severe shocks generated by means other than the vehicle, for example, the depth charging of a submarine. To absorb these severe shocks, preloaded liquid springs may be used to support the inner tube within the outer tube. These springs are preloaded to such an extent that they normally act as a rigid connection between the inner and the outer tubes. Consequently, vehicle induced vibrations are not attenuated by the liquid springs but, to the contrary, are amplified as they pass through the missile launcher structure to the missile itself. The missile guidance system as well as many other missile components cannot withstand any substantial vibration Without being adversely affected thereby. Consequently, these vibrations become a limiting factor in the performance of a vehicle launched missile system. Since these vibrations are primarily generated by vehicle movement and by the vehicle power plant,'the speed of the vehicle must be substantially restricted in order to prevent vibration damage to the missile and its components. Restricting the speed of such a vehicle, obviously, greatly reduces its invulnerability.

Accordingly, one object of the present invention is to provide a means to protect a missile from launcher induced vibrations.

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Another object of the present invention resides in the provision of a means which will attenuate vibrations being transferred to a missile from its launcher.

Still another object of the present invention provides a means to absorb vehicle induced Vibrations in a missile launching system.

A further object of this invention is to provide a vibration absorbing means for a missile launching system which is reliable in operation and relatively inexpensive in cost.

Still a further object of the present invention resides in the provision of a liquid spring which is operable to absorb severe shock as well as loW amplitude high frequency vibration.

Other objects and many of the attendant advantages of this invention will be readily appreciated as the same becomes better understood by reierence to the following detailed description when considered in connection with the accompanying drawings wherein:

FIG. 1 is a transverse cross-sectional view of a typical ballistic missile launching vehicle;

FIG. 2 is a sectional view of a hydraulic spring device incorporating the present invention; and

FIG. 3 is an exploded sectional view of the end of the hydraulic spring which incorporates the vibration absorbing means.-

FIG. 1 illustrates one embodiment of the present invention, and more specifically, it discloses a cross-sectional view of a ballistic missile launching submarine 11. As the missile launching systems in the submarine are identical the description which follows hereinafter will describe a single launching system.

A missile 12 is positioned in the missile launching system which has its upper portion covered by the hatch 14. Each missile launching system includes an outer tube 15 which has resiliently mounted therein an inner tube 16. The tubes are provided with an opening 17 which is utilized to gain access to the missile guidance package, not shown. The missile 12 is ejected from the inner tube 16 when high pressure fluid is released from the flask 18. This fluid pressure is controlled by a fluid valve 22 positioned in the conduit 19 which connects the fluid flask 18 at the lower portion of the launching system. Hydraulic springs 21 resiliently support the inner tube 16 within the outer tube 15 thereby isolating the missile 12 from sudden and severe shocks, for example, depth charges.

As illustrated in FIG. 2, each liquid spring 21 consists of an outer cylinder 36 which contains two piston assemblies: compression 3t) and tension 40. The compression piston 39 assembly includes the piston rod 31 which extends out through the front seal 32 and attaches to the launch tube clevis-type connector 34 with a clevis pin not shown. The compression piston head 39 attaches to the piston rod 3-1 and slides within the hollow tension piston body 48 which, in turn, slides within the outer cylinder 36. The tension piston 40 is stepped and its smaller diameter 41 extends through the back seal 42 into the air space 43 within the end bell 45, and the terminal assembly 46. The cylinder 36 can be connected to a fitting on the mount tube with any conventional means such as the ball joint 49. A threaded retainer bushing 47 in the hollow end of the tension piston 48 retains the compression piston 30 within the tension piston 40. a

The compression and tension pistons divide the space of the liquid spring into three compartments or chambers, A, B, and C. Chamber A is connected with chamber C through an orifice 50 in the tension piston. Chamber B is connected with chamber C through a port 51 in the tension piston wall. When the launcher tube 16 is in normal position, the fluid volume within the cylinder is at its maximum, and there is equal pressure in'all three chambers. When the compression piston rod 31 is pushed Patented May 11, 1965 into the cylinder of tension piston 40, only the compression piston 30 moves, while the tension piston 40 remains in normal position against a collar 48 machined on the bore of the cylinder 36. This increases the pressure in all three chambers by decreasing the total volume within the cylinder. The decrease in total volume is equal to the volume of piston rod 31 which enters the cylinder 36. The increase in pressure throughout the cylinder 36 provides the restoring force, tending to return the compression piston 30 to its normal position.

When the piston rod 31 is pulled out of the cylinder 36, the compression piston 30 engages the retainer bushing 47 in the tension piston 40 and pulls the tension piston 40 with it in the same direction; this movement of the tension piston 40 withdraws its extension 41 through the back seal 42 in the back packing ring. This also increases the pressure in all three chambers by decreasing the total volume within the cylinder 36. The decrease in total volume is equal to the ditference between the volume of piston rod 31 pulled out of the cylinder and the volume of the larger diameter tension piston extension 4-1 which is pulled into the cylinder 36. The increase in pressure throughout the cylinder 36 provides the restoring force, tending to return both tension 40 and compression 30 pistons to their normal positions.

Fluid is displaced from chamber A to chambers B and C or vice versa with either extension or compression of the liquid spring. The displaced fluid passes through the port 51 during a compression cycle and the orifice 50 during a tension cycle. The pressure differential across the port 51 does not affect the pressure relationship between chambers B and C, which remain under approximately equal pressure at all times because of the relatively large port 51. Under slow rates of piston rod 31 movement, the pressures in the three chambers remain approximately equal. Rapid piston rod movement, however, requires correspondingly large fluid velocities through the orifice and port, resulting in a pressure differential across the orifices. This pressure differential acts on the compression and tension pistons and creates a force which adds to the restoring force 011 the outstroke and subtracts from the restoring force on the return stroke. The additional force is the damping factor of the liquid spring, and its magnitude is proportional to the velocity of piston travel and the length of the excursions. This damping force enables the system to come to rest rapidly with a relatively small number of oscillations following a shock. The liquid springs are self-contained shock absorbing units which are filled with a compressible silicone oil or its equivalent. A check valve 60 at the charging port 61 prevents leakage of fluid and loss of pressure. A bleed valve 62 is provided for purposes of checkout. The springs 21 are charged to working pressure through the check valves 60.

The lower end of the liquid spring assembly, as is shown in FIGS. 2 and 3, contains the small amplitude high frequency vibration absorbing assembly. This assembly has a member 70 threadedly engaging the internal threads of the cylinder 36. A tubular shaped member 71 engages the projection 72 of the member 70. The vibration attenuating material 73 surrounds the tubular shaped member 71, shown in FIG. 3. The annular shaped member 74 threadedly engages the tubular shaped member 71 in a manner to restrict the longitudinal movement of the material 73. The bell end member 45 of the liquid spring 21 threadedly engages the outer portion of the annular member 74. The vibration absorbing material 73 may be of any conventional type, for example, a knitted steel wire material or a rubber impregnated canvas material.

In operation, when the vehicle in the missile launching system is mounted it is subjected to a severe shock, for example collision of the vehicle or depth charging, the liquid springs 21 protect the inner tube 16 and conse quently the missile 12 from being subjected to this severe shock. These liquid springs 21 perform in a manner described hereinbefore. However, when the vehicle induced vibration of a low amplitude high frequency are transmitted through from the outer tube to the inner tube they would normally be amplified. However, with the present invention these high frequency, vehicle generated vibrations are attenuated. More specifically, as these vehicle induced vibrations pass through the liquid spring 21 the vibration attenuating material 73 substantially absorbs these vibrations thereby protecting the inner tube 16 and the missile 12 from possible damage, and when the system is subjected to severe shock, the vibration absorbing material 73 advantageously reduces the jerk which occurs when the liquid springs initially begin to absorb the shock. This jerk is believed due to the looseness of the mechanical connections within the launching system; that is, the looseness to be absorbed before the liquid springs become operational.

While the invention has been described with reference to a ballistic missile firing submarine, it is capable of being used in conjunction with any mobile launching system. The present invention enables such a vehicle to move at speeds which are restricted by vehicle generated vibrations.

Obviously many modifications and variations of the present invention are possible in the light of the above teachings. It is therefore to be understood that within the scope of the appended claims the invention may be practiced otherwise than as specifically described.

What is claimed is:

1. A liquid spring comprising, an outer cylinder having a bore, a pair of seals affixed in said bore and forming an enclosed chamber for containing a fluid, a piston slideably retained within said bore, said piston having a counterbore therein, a piston rod having a plunger head slideably received in the counterbore of the piston for limited movement relative thereto and having the rod portion thereof extending through one of said seals, first attaching means for connection to a load to be springaction controlled secured to the other end of said piston rod, a second rod attached to the other end of said piston and configured to have a greater cross-sectional area than that of said piston rod, said second rod extending through the other of said seals, said piston having an orifice therethrough for establishing fluid communication between the portion of the chamber surrounding the piston rod and the portion of the chamber surrounding said second rod, second attaching means afiixed to said outer cylinder remote from the first attaching means in order that application of a tensile load to the spring through said attaching means functions to draw said piston rod out of said chamber and said second rod into said chamber, thereby decreasing the volume by virtue of the differential in displacements thereof and effecting an increase in the pressure therein thereby applying a restoring force to said piston.

2. A liquid spring according to claim 1 and further comprising a retainer in said counterbore for preventing removal of said plunger head therefrom, said piston having a fluid port connecting said counterbore to said chamber, said port being located at a position remote from said retainer, and collar means in said bore for limiting the movement of said second rod out of said chamber, whereby when a compressive load is applied to said attaching means said collar means will prevent movement of said second rod, and said piston rod and plunger head will move into said counterbore decreasing the volume of said chamber and increasing the pressure of the fluid therein thereby applying a restoring force to said piston rod.

3. A liquid spring according to claim 2 and further comprising a first member attached to said outer cylinder, a tubular member slideably retained on said outer cylinder by said first member, an annular member attached to said tubular member, said first member, said tubular member and said annular member forming a partially Heiss 26764 Carbon 26764 Siegel et a1. 891.7 Staltz 26764 Werle et a1. 89-1 Smith 267--64 Heiss et a1. 267-35 ARTHUR L. LA POINT, Primary Examiner.

ARTHUR M. HORTON, SAMUEL BOYD, BENJAMIN A. BORCHELT, Examiners. 

1. A LIQUID SPRING COMPRISING; AN OUTER CYLINDER HAVING A BORE, A PAIR OF SEALS AFFIXED IN SAID BORE AND FORMING AN ENCLOSED CHAMBER FOR CONTAINING A FLUID, A PISTON SLIDEABLY RETAINED WITHIN SAID BORE, SAID PISTON HAVING A COUNTERBORE THEREIN, A PISTON ROD HAVING A PLUNGER HEAD SLIDEABLY RECEIVED IN THE COUNTERBORE OF THE PISTON FOR LIMITED MOVEMENT RELATIVE THERETO AND HAVING THE ROD PORTION THEREOF EXTENDING THROUGH ONE OF SAID SEALS, FIRST ATTACHING MEANS FOR CONNECTION TO A LOAD TO BE SPRINGACTION CONTROLLED SECURED TO THE OTHER END OF SAID PISTON ROD, A SECOND ROD ATTACHED TO THE OTHER END OF SAID PISTON AND CONFIGURED TO HAVE A GREATER CROSS-SECTIONAL AREA THAN THAT OF SAID PISTON ROD, SAID SECOND ROD EXTENDING THROUGH THE OTHER OF SAID SEALS, SAID PISTON HAVING AN ORIFICE THERETHROUGH FOR ESTABLISHING FLUID COMMUNICATION BETWEEN THE PORTION OF THE CHAMBER SURROUNDING THE PISTON ROD AND THE PORTION OF THE CHAMBER SURROUNDING SAID SECOND ROD, SECOND ATTACHING MEANS AFFIXED TO SAID OUTER CYLINDER REMOTE FROM THE FIRST ATTACHING MEANS IN ORDER THAT APPLICATION OF A TENSILE LOAD TO THE SPRING THROUGH SAID ATTACHING MEANS FUNCTIONS TO DRAW SAID PISTON ROD OUT OF SAID CHAMBER AND SAID SECOND ROD INTO SAID CHAMBER, THEREBY DECREASING THE VOLUME BY VIRTUE OF THE DIFFERENTIAL IN DISPLACEMENTS THEREOF AND EFFECTING AN INCREASE IN THE PRESSURE THEREIN THEREBY APPLYING A RESTORING FORCE TO SAID PISTON. 